| abstract |
The invention aims at providing a composition for rubber stoppers which is easy of molding and excellent in sealing properties and gas barrier properties, little dissolves in contents, and exhibits favorable needle penetration; and rubber stoppers for medical use, made by using the same. The aim is attained by a composition which is prepared by dynamically crosslinking an alkenyl-terminated isobutylene polymer with a hydrosilyl compound in the presence of a polyolefin and adding a softener and which has a prescribed make-up. The composition may further contain a block copolymer composed of both a polymer block (a) made mainly from an aromatic vinyl compound and a polymer block (b) made mainly from isobutylene or a lubricant. |